Commit a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer
in use") changed the behavior of lockdep_free_key_range() from
unconditionally zapping lock classes into only zapping lock classes if
debug_lock == true. Since the new behavior can cause cat /proc/lockdep to
crash due to a NULL pointer dereference, restore the pre-v5.1 behavior.Cc: Thomas Gleixner <[email protected]> Cc: Will Deacon <[email protected]> Cc: Waiman Long <[email protected]> Cc: shenghui <[email protected]> Reported-by: shenghui <[email protected]> Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1. Signed-off-by: Bart Van Assche <[email protected]> --- kernel/locking/lockdep.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 34cdcbedda49..70480e4f8f5d 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -4689,8 +4689,7 @@ static void free_zapped_rcu(struct rcu_head *ch) return; raw_local_irq_save(flags); - if (!graph_lock()) - goto out_irq; + arch_spin_lock(&lockdep_lock); /* closed head */ pf = delayed_free.pf + (delayed_free.index ^ 1); @@ -4702,8 +4701,7 @@ static void free_zapped_rcu(struct rcu_head *ch) */ call_rcu_zapped(delayed_free.pf + delayed_free.index); - graph_unlock(); -out_irq: + arch_spin_unlock(&lockdep_lock); raw_local_irq_restore(flags); } @@ -4744,21 +4742,15 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size) { struct pending_free *pf; unsigned long flags; - int locked; init_data_structures_once(); raw_local_irq_save(flags); - locked = graph_lock(); - if (!locked) - goto out_irq; - + arch_spin_lock(&lockdep_lock); pf = get_pending_free(); __lockdep_free_key_range(pf, start, size); call_rcu_zapped(pf); - - graph_unlock(); -out_irq: + arch_spin_unlock(&lockdep_lock); raw_local_irq_restore(flags); /* @@ -4911,9 +4903,7 @@ void lockdep_unregister_key(struct lock_class_key *key) return; raw_local_irq_save(flags); - if (!graph_lock()) - goto out_irq; - + arch_spin_lock(&lockdep_lock); pf = get_pending_free(); hlist_for_each_entry_rcu(k, hash_head, hash_entry) { if (k == key) { @@ -4925,8 +4915,7 @@ void lockdep_unregister_key(struct lock_class_key *key) WARN_ON_ONCE(!found); __lockdep_free_key_range(pf, key, 1); call_rcu_zapped(pf); - graph_unlock(); -out_irq: + arch_spin_unlock(&lockdep_lock); raw_local_irq_restore(flags); /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */ -- 2.21.0.196.g041f5ea1cf98
